1. Field of Invention
This invention relates generally to a process for extracting type I collagen from an avian source, and more particularly to a process for processing poultry feet to isolate therefrom type I collagen useful for medical and biotechnology applications, cosmetic formulations and food products.
2. Status of Prior Art
Collagen is a substance which accounts for about thirty percent of the total human body protein. Collagen, which has a characteristic amino acid composition, forms the fibrillar component of soft connective tissues such as skin, ligament and tendon, and is the major component of the organic matrix of calcified hard tissues such as bone and dentine.
There exist at least twelve genetically distinct types of collagen. The most familiar, type I, consists of three polypeptide chains. Two chains are identical and are called .alpha. 1(I); the third being called .alpha. 2(I). I collagen forms the major portion of the collagen of both soft (skin, tendon) and hard (bone and dentine) connective tissue. Type II collagen is the major collagen of cartilage and is composed of three .alpha. (II) chains. Type III collagen is composed of three .alpha. 1(III) chains and is found in blood vessels, wounds, and certain tumors. Reticulin fibers appear to be identified with type III collagen. Basement membrane collagens are classified as type IV.
The intercellular substances of connective tissue are classified as either amorphous or fibrous. The former exist as firm or soft gels. These are proteoglycans containing bound water which permits diffusion to take place through them. Fibrous intercellular substances are commonly immersed in the amorphous type and assume various forms, such as the white fibers of collagen, yellow fibers constituting an elastin, and reticular fibers in the form of lacy networks that give intimate internal support to cells. Connective tissue cells that generate intercellular substances thereafter lie within the substances they have formed.
Type I collagen, which is a biodegradable polymer, has been used as a plasma expander, a vehicle for drug delivery, as a vitreous body replacement, a hemostatic agent, a suture material, a corneal replacement, a hemodialysis membrane, a wound dressing, an artificial skin, and a hernia patch, as well as a vessel prosthesis, a vaginal contraceptive and an injectable agent for tissue augmentation (Pachence et al., Medical Device and Diagnostic Industry, 9:49 (1987)). In some of these applications, the collagen is reconstituted and cross-linked into an insoluble form.
Collagenous materials have been used for centuries for tissue repair (see Pachence et al., Medical Device and Diagnostic Industry, 9:49 (1987)). The biological properties of collagen include its ability to stimulate wound healing (Doillon and Silver, Biomaterials, 7:3 (1986)), to promote cell attachment (Kleinman et al., J. Cell Biology, 88:473 (1981)), to attract inflammatory cells (Hopper et al., Immunology, 30:249 (1976)), and to act as a substrate that supports new cell growth (Elsdale and Bard, J. Cell Biology, 54:626 (1976).
Cell infiltration and tissue attachment to collagenous matrices is an important characteristic of type I collagen (Yannas, in The Surgical Wound, ed. Dineen and Hildick-Smith, Lea and Febeger, Inc., p. 171 (1981); and Doillon et al., Scanning Electron Microscopy, 3:1212 (1984)).
Despite its significant advantages, the commercial success of collagen-based materials has been limited to a few specialized products that make use of collagen's unique properties. The major reasons for the lack of commerciall available collagen-based medical and biotechnology products are as follows:
1. The high cost of preparation of pure type I collagen from bovine and porcine sources as compared to the cost of synthetic biomaterials. PA1 2. The variability of isolated collagen; PA1 3. The difficulties of handling and storing collagen as compared to synthetic materials.
Of prior art background interest are the Robertson U.S. Pat. Nos. 4,216,204; 4,555,303 and 4,094,973, which disclose producing protein hydrolysate from poultry feet.